|Episode #|Original air date (UK)|Episode title|Guest cast|DVD # 1|
|---|---|---|---|---|
|1-01|22 October 1976|"The Eagle's Nest"|Peter Cushing, Derek Farr, Frank Gatliff, Trevor Baxter, Jerold Wells, Sydney Bromley, Peter Porteous|1.01|
|1-02|29 October 1976|"House of Cards"|Peter Jeffrey, Mark Burns, Annette Andre, Jeremy Wilkin, Frank Thornton, Lyndon Brook, Derek Francis, Gordon Sterne, Anthony Bailey|1.03|
|1-03|5 November 1976|"The Last of the Cybernauts?"|Robert Lang, Oscar Quitak, Basil Hoskins, Robert Gillespie, Gwen Taylor, Ray Armstrong, Martin Fisk|1.04|
|1-04|12 November 1976|"The Midas Touch"|John Carson, Ronald Lacey, Ed Devereaux, Pik-Sen Lim, Geoffrey Bateman, Tim Condren, Chris Tranchell, David Swift|1.02|
|1-05|19 November 1976|"Cat Amongst the Pigeons"|Vladek Sheybal, Basil Dignam, Paul Copley, Kevin Stoney, Hugh Walters, Brian Jackson, Gordon Rollings|1.06|
|1-06|26 November 1976|"Target"|Keith Barron, Frederick Jaeger, Robert Beatty, Bruce Purchase, Roy Boyd, Deep Roy, John Paul, Malcolm Stoddard|1.07|
|1-07|3 December 1976|"To Catch a Rat"|Ian Hendry, Barry Jackson, Edward Judd, Dallas Cavell, Jo Kendall|1.05|
|1-08|10 December 1976|"The Tale of the Big Why"|Derek Waring, Jenny Runacre, Roy Marsden, George A. Cooper, Geoffrey Toone, Gary Waldhorn|1.09|
|1-09|17 December 1976|"Faces"|David de Keyser, Edward Petherbridge, Richard Leech, Michael Sheard, Donald Hewlett, Neil Hallett, David Webb, J. G. Devlin|1.08|
|1–10|21 December 1976|"Gnaws"|Julian Holloway, Peter Cellier, Jeremy Young, Patrick Malahide, W. Morgan Sheppard, Keith Marsh|1.11|
|1–11|7 January 1977|"Dirtier by the Dozen"|John Castle, Shaun Curry, Alun Armstrong, Michael Barrington, Brian Croucher, Stephen Moore, John Forbes-Robertson, David Purcell|1.13|
|1–12|14 January 1977|"Sleeper"|Keith Buckley, Sara Kestelman, Prentis Hancock, Mark Jones|1.12|
|1–13|21 January 1977|"Three-Handed Game"|Stephen Greif, Tony Vogel, David Wood, Ronald Leigh-Hunt, Annie Lambert, Hugh Morton, John Paul|1.10|

Question: what is the least number of guest casts on an episode?
Answer: 4